C−−H activation on aluminum-vanadium bimetallic oxide cluster anions.

Aluminum-vanadium bimetallic oxide cluster anions (BMOCAs) have been prepared by laser ablation and reacted with ethane and n-butane in a fast-flow reactor. A time-of-flight mass spectrometer was used to detect the cluster distribution before and after the reactions. The observation of hydrogen-containing products AlVO(5)H(-) and Al(x)V(4-x)O(11-x)H(-) (x=1-3) strongly suggests that AlVO(5)(-) and Al(x)V(4-x)O(11-x)(-) (x=1-3) can react with ethane and n-butane by means of an oxidative dehydrogenation process at room temperature. Density functional theory studies have been carried out to investigate the structural, bonding, electronic, and reactive properties of these BMOCAs. Terminal-oxygen-centered radicals (O(t)(.)) were found in all of the reactive clusters, and the O(t)(.) atoms, which prefer to be bonded with Al rather than V atoms, are the active sites of these clusters. All the hydrogen-abstraction reactions are favorable both thermodynamically and kinetically. To the best of our knowledge, this is the first example of hydrogen-atom abstraction by BMOCAs and may shed light on understanding the mechanisms of C−−H activation on the surface of alumina-supported vanadia catalysts.